1. Field of the Invention
The present invention relates to a member for a production device for producing Group III--V compound semiconductors, and a production device using the same.
2. Description of Related Art
As a material of light-emitting devices such as a light-emitting diode (hereinafter sometimes referred to as "LED") in the ultraviolet, blue or green color range or a laser diode in the ultraviolet, blue or green color range, a Group III--V compound semiconductor represented by the general formula In.sub.x Ga.sub.y Al.sub.z N (provided that x+y+z=1, 0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, and 0.ltoreq.z.ltoreq.1) has hitherto been known.
Examples of processes for producing a Group III--V compound semiconductor include the molecular beam epitaxy (hereinafter sometimes referred to as "MBE") process, the organometallic vapor phase epitaxy (hereinafter sometimes referred to as "MOVPE") process, the hydride vapor phase epitaxy (hereinafter sometimes referred to as "HVPE") process and like processes. Among them, the MOVPE process is particularly preferred because uniform formation of layers in a large area can be generally conducted in comparison with the MBE and HVPE processes.
In the vapor phase deposition process for producing a compound semiconductor, a member of the production device is exposed to an atmosphere of raw gases (e.g. hydrogen, organometallic compounds, ammonia gas, etc.) which have a large reactivity at high temperature. Therefore, it is necessary that the members used in the production device be composed of a material which has high resistance to these raw gases and which emits a minimal amount of impurities so that a high-purity semiconductor can be grown.
Graphite is often used in a production device for semiconductors other than the compound semiconductor because of various features such as its stability at high temperature, its ability to be easily heated due to its high absorption efficiency of high frequency electromagnetic waves or infrared rays or by Joule heat of the current through the graphite itself, its emission of small amounts of impurities and the like. However, it is known that graphite has high reactivity to ammonia, especially at a high temperature, and is drastically deteriorated, upon exposure to a high-temperature ammonia atmosphere. Therefore, graphite is generally used after coating the surface of the graphite with a chemically stable material (e.g. SiC, etc.) in a thickness of about 100 .mu.m.
However, problems occur in that the coating material such as SiC is gradually cracked or pinholes develop when it is exposed to a high-temperature (not less than 1000.degree. C.) atmosphere for a long time or when a cycle of heating to a temperature of not less than 1000.degree. C. and cooling to room temperature is repeated, even if graphite coated with SiC is used as the material for the member. Another problem is that the coated SiC cannot be used for the sliding part of the member because the surface thereof is not smooth.
On the other hand, a SiC-sintered member has high resistance to ammonia, but has a problem in that it cannot be easily formed into a complicated form because SiC is a remarkably hard material.